Mesa Piezoelectric Resonator Etching Depth for Stable CI
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Solution Overview
Problem
Mesa-shaped piezoelectric resonator elements face challenges in miniaturization due to decreased vibrational energy concentration and increased susceptibility to unnecessary modes and etching variations, leading to deteriorated vibration characteristics and reduced crystal impedance (CI) values.
Innovation Solution
The etching depth of the mesa-shaped piezoelectric resonator element is optimized to a minimum value based on the relationship y = -1.32 × (x/t) + 43 ± 5%, where x is the length of the substrate's long side and t is the resonator section's thickness, to maintain flat CI characteristics and reduce unnecessary vibrations, while keeping the fineness ratio x/t below 30 to ensure effective resonator formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the etching depth is increased to reduce CI value, then the CI value decreases, but unnecessary modes are coupled with the thickness sliding mode causing vibration characteristic deterioration
Solution Approach 1:
The patent optimizes the etching depth parameter to a specific range (0.5-2.0 μm) that balances CI value reduction with maintaining vibration characteristics. This parameter optimization prevents excessive etching that would cause unnecessary mode coupling while still achieving sufficient CI value reduction for miniaturized substrates.
2Length of stationary object
If the etching time is increased to increase the etching depth, then the etching depth increases, but undesired etching occurs with degradation of the protective film
Solution Approach 1:
The patent applies a protective film before the etching process to prevent undesired etching. By preparing this protective layer in advance, the patent ensures that only the intended areas are etched to the required depth, preventing shape variations and maintaining manufacturing precision even when etching is performed for sufficient depth.
3Area of moving object
If the area of the piezoelectric substrate is decreased for miniaturization, then the resonator size is reduced, but the difference in mass within the substrate decreases making it difficult to concentrate vibrational energy
Solution Approach 1:
The patent creates a mesa-shaped structure with different thicknesses in different regions of the substrate. The resonator section has a greater thickness than the peripheral section, creating local mass concentration in the resonator area. This local quality variation enables effective vibrational energy concentration even in miniaturized substrates where overall mass differences are small.
Solution Approach 2:
Instead of relying on planar mass distribution, the patent introduces a vertical dimension by creating a mesa structure with varying thickness. This dimensional transition from 2D to 3D structure allows effective mass concentration and vibrational energy confinement in the resonator section, solving the energy concentration problem in miniaturized devices.
4Ease of manufacture
If a mesa shape with clear level difference is used for easy processing, then mass production is enabled, but unnecessary modes are coupled with the thickness sliding mode
Solution Approach 1:
The patent optimizes the etching depth parameter within a specific range (0.5-2.0 μm) that maintains the mesa structure's manufacturing simplicity while preventing excessive level differences that would cause mode coupling. This parameter control allows the clear level difference to remain for easy processing without triggering unwanted vibrations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration minimizes etching time, reduces shape variations, and maintains favorable vibration characteristics by suppressing unnecessary modes, thereby enhancing the design margin and productivity of the piezoelectric resonator elements.
Implementation Method 1
a piezoelectric resonator element in which a resonator section having a greater thickness than a peripheral section is formed on a board surface of a piezoelectric substrate
Data Source
AI summary
A mesa-shaped piezoelectric resonator element including a resonator section having a thicker thickness than a peripheral section on the board surface of a piezoelectric substrate formed in a rectangular shape, wherein, when the length of the long side of the piezoelectric substrate is x and the board thickness of the resonator section is t, etching depth y of a level-difference section is set to fulfill a relationship in the following equation, based on the board thickness t.y=-1.32×(xt)+43±5(%)